Olive Ridley turtle eggs are sensitive to temperature — and climate change isn't doing them much good
In a first, Tamil Nadu has announced the setting up of climate-resilient hatcheries that will ensure just the right temperatures for their eggs to hatch
How do Olive Ridley turtles confront the realities of global warming?
“Every year, the struggle intensifies for them,” said S Thangavelu, a seasoned fisherman from Cuddalore. “Caught in fishing nets of fine mesh, or losing their way to the nesting beaches, the challenges are increasing. And as we ourselves grapple with the rising sea temperatures, it's daunting to consider the toll it's taking on these sea creatures.”
“High temperatures significantly raise mortality rates among Olive Ridley turtle hatchlings,” Srinivas R. Reddy, principal chief conservator of forests and chief wildlife warden, Tamil Nadu forest department, concurred.
In fact, the survival of the species depends on the fragile balance of temperature within their hatcheries. “This delicate balance is crucial, with warmer nests birthing females and cooler ones males, steering the species' survival,” explained Dr R Suresh Kumar, senior scientist at the Wildlife Institute of India (WII), Dehradun.
Temperature around 31.5 degrees Celsius ± 1.5 degrees Celsius is said to be the pivotal temperature where the sex ratio is likely to be 50:50 for olive ridley turtles, Kumar added. “The difference of a few degrees can decide the fate of generations," Kumar said.
“The sex of sea turtle hatchlings is determined by the temperature in the nest during embryonic development. In all sea turtles, higher temperature produces females while the lower temperature produces males. For Olive ridley sea turtles, temperatures more than 32 degrees are known to produce all females while at temperatures below 28 degrees, all hatchlings are males,” he said.
To mitigate the impact of escalating temperatures on sea turtles, Tamil Nadu recently introduced climate-resilient hatcheries. Reddy initiated the request for these kinds of hatcheries to be set up, and WII recently began providing technical support to the TN forest department.
Last month, their efforts paid off. Additional chief secretary (environment, climate change and forests) Supriya Sahu announced Tamil Nadu's government order to establish 10 climate-resilient turtle hatcheries across eight districts sanctioned at a cost of ₹10 lakh, a pioneering endeavour for marine conservation, especially in response to climate change.
Protected under Schedule I of the Wildlife (Protection) Act, 1972, India is home to the largest known nesting population of Olive Ridley turtles.
What makes hatcheries climate-change resilient?
Climate-resilient hatcheries are facilities aimed at safeguarding marine species, notably sea turtles, from climate change impacts. These hatcheries replicate natural nesting conditions, control temperature to ensure a balanced gender ratio among hatchlings and manage humidity to prevent eggs from drying out. They offer protection against extreme weather events, such as storms, that could destroy nests.
“Our approach is straightforward: we create protective environments that closely mimic their natural habitats. The critical addition to these hatcheries is our ability to monitor and adjust temperature and humidity—key factors that influence the gender of the hatchlings,” Reddy said.
Equipped with monitoring tools such as data loggers, these hatcheries gather information to refine conservation efforts, while also shielding eggs from predators, including birds, dogs, and humans. “With these measures, we aim to elevate the hatching success to beyond 90%,” said Reddy, adding, “In all these hatcheries, we strictly regulate temperatures, never allowing them to exceed 35-40 degrees Celsius, a threshold often surpassed on several beaches statewide.
So far, permanent and semi-permanent climate-resilient hatcheries have been set up at Marakkanam in Villupuram District, the Pichavaram range of Cuddalore division, and two sites in the Nagapattinam division within the Mayiladuthurai district. The Marakkanam hatchery, alongside its counterparts, has already nurtured over 9,000 eggs in Nagapattinam and released about 2,000 hatchlings from the MGR Thittu site in Vellar sea shore.
Climate change hurts marine species
India's coastal waters are home to five of the world's sea turtle species. This diverse group includes the Olive Ridley, Green, Hawksbill, Leatherback, and Loggerhead turtles. These species display remarkable variation in size and weight, ranging from the smaller Olive Ridley turtles, averaging 25-46 kg with a carapace length of 60-70 cm, to the massive Leatherback turtles, which can weigh up to 650 kg and measure 2.13 m. Despite being adeptly adapted to aquatic life with streamlined bodies and large flippers, sea turtles retain a crucial connection to the land. Female turtles must venture onto beaches to lay their eggs, ensuring that even the mightiest sea turtles are born from the humble beginnings of sand-bound nests.
Reddy highlighted two major changes observed along the Tamil Nadu coast this year. First, there is an observable shift in the nesting patterns and timings that suggests a changing climate may be at play. “Earlier there were larger numbers towards Chennai but now the turtles prefer the southern beaches beyond Chennai, such as Cuddalore and further south,” he said.
The second is how the nesting season is starting later, shifting from December to January, with a notable 20-day delay. “This delay could influence the hatchlings' survival rates, as late-season nests often have lower success. Typically, the season used to wrap up by the end of March, but now it's extending further. We're adapting to these changes, prepared to protect and monitor these nests for as long as necessary,” said Reddy.
Meanwhile, global climate phenomena such as El Niño (periodic warming of sea-surface temperatures in the central and eastern Pacific Ocean, affecting global weather patterns) and La Niña (cooling of sea-surface temperatures in the central and eastern Pacific Ocean, influencing global weather patterns with effects often opposite to those of El Niño) no longer just affect weather patterns but threaten the reproductive cycles of these turtles as well.
“Reproductive investment of sea turtles is very likely influenced by the availability of food resources at their foraging grounds and this is in turn influenced by the global weather systems such as El Niño and La Niña. So, low intensity of nesting recorded at a nesting beach in a certain year is very likely a result of less number of turtles arriving in the area to nest,” said Kumar.
The WII is in the process of conducting an assessment with the aim of creating a national sea turtle database to study the patterns of turtle nesting observed along the Indian coast. The report is expected later this year.
This assessment, backed by the Ministry of Environment, Forests and Climate Change (MoEFCC) under the Integrated Development of Wildlife Habitats scheme, represents a strategic endeavour to map and monitor India's sea turtle populations. “We are pinpointing the most critical nesting sites along our entire coastline, where turtle nesting activity is at its peak. Our focus is not just to document these key areas but to ensure they are given the attention and protection needed for sustained long-term monitoring,” Kumar said.
The last time such a detailed assessment was developed was in 2004. In 2021, the MoEFCC published the National Marine Turtle Action Plan (2021-2026), with the aim to conserve marine turtles and their habitats by identifying threats and looking at regional and national level cooperation. The plan also released close to 40 important turtle habitats across Andaman and Nicobar Islands, Odisha, Lakshadweep, Andhra Pradesh, Tamil Nadu, Maharashtra, Goa, Gujarat, and Puducherry.
Virendra Tiwari, director, WII said, “With climate change altering coastal landscapes and the increasing threats of overfishing and pollution, identifying and protecting these nesting sites become crucial for the survival of turtle species, especially the Olive Ridley. This effort will allow us to prioritise conservation actions where they are most needed, ensuring a safer future for all turtle species that inhabit our waters.”
A state of hatcheries
Tamil Nadu's efforts in marine wildlife conservation have resulted in the establishment of 49 hatcheries across the state between 2023 and till March 25, 2024 (this does not include the 10 climate-resilient hatcheries planned across eight districts). These hatcheries have collected 2,181 nests, culminating in the safeguarding of 239,677 eggs. Of these, a significant number of hatchlings, totalling 33,221, have been released into their natural habitat.
“The numbers are expected to rise further as the season progresses,” said Reddy, adding that the efforts have been possible because of the 121 forest staff members working alongside a formidable contingent of 900 volunteers.
In the last week of March, divisional forest officers met Kumar to plan more climate-resilient hatcheries. “While the purpose has been more on nest protection and hatching success, it is crucial to understand where the turtles are nesting and this is likely to vary across months given rising temperatures. During the hottest months, nests might be located closer to areas with higher moisture (river mouth, high tide line). I have advised the officers to spend more time on documentation of nest locations going forward,” he said.
Since 2023, there have been 1,150 turtle mortalities in eight of Tamil Nadu’s districts, including Kanyakumari (588), Ramnad (283), Chennai (127), and Cuddalore (116) among others. “This includes both onshore and offshore threats, human-induced and natural, resulting in such deaths,” said a forest official from Tamil Nadu.
“While coastal development activities are known to impact turtle nesting, the true scale of these impacts is not known. On the other hand, the impact of climate change on nesting along the Indian coastline is still to be discerned, particularly since there has been no baseline and long-term monitoring data sets,” said Kumar.
In previous years, over 183,000 hatchlings have been released into the sea. The department established 35 hatcheries throughout the state and collected 216,000 eggs.
Besides climate-resilient hatcheries, it is also important to identify, record, and secure nesting sites. “Key efforts include eliminating or minimising the loss of beaches due to coastal erosion, casuarina plantation and beach armouring, and securing the turtle nests from feral dog predation. Additionally, ensuring the nesting beaches are free of artificial light (light pollution), is critical. The idea is to identify turtle nesting zones along the 7500 km Indian coastline where the above strategies need to be adopted,” said Kumar.